1. Field of the Disclosure
The present disclosure relates generally to the shale shaker screens used to filter solids out of drilling mud.
2. Description of Related Art
When drilling a well (e.g., for oil or gas), a drill bit is attached to the end of a drill string and drills a hole through the subsurface to access the oil or gas reservoir. Drilling fluid is used during drilling operations. Drilling fluid comprises, for example, a finely ground clay base material to which various chemicals and water are added to form a viscous fluid designed to meet specific physical properties appropriate for the subsurface conditions anticipated. This drilling fluid is pumped down the hollow drill pipe, through the drill bit and returned to the surface in the annular space between the drill pipe and the well bore.
The drilling fluid serves three main purposes. First, it aids in cooling the drill bit and thereby increasing its useful life. Second, the mud flushes the cuttings or “solids” from the well bore and returns them to the surface for processing by a solid control system. Third, the mud leaves a thin layer of the finely ground clay base material along the well bore walls which helps prevent caving in of the well bore wall.
Although often referred to simply as “mud,” the drilling fluid is a complex composition which must be carefully engineered and tailored to each individual well and drilling operation. The drilling fluid is costly and, thus, is cleaned and reused in a closed loop system in which a solids control system and a shaker play important roles.
A shaker, often referred to as a “shale shaker,” is part of a solids control system used in oil and gas drilling operations to separate the solid material (“solids”), removed from the well bore by the drilling operation, from the drilling mud. For the drilling fluid to be used and reused, it must be processed after returning from the well bore to remove the aforementioned solids and maintain its proper density, often expressed as pounds per gallon or “mud weight”, i.e., 10 lb./gal. mud or “10 lb. mud”. The first step in processing the returned drilling fluid is to pass it through a shaker. The returned drilling fluid from the flow line flows into a possum belly, a container mounted at one end of the shaker, and then flows over one or more screens. A shaker includes a support frame on which the shaker screen is mounted. One or more motors in the shaker causes the screen assemblies to vibrate or oscillate, depending on the type of motors utilized. The vibrating action of the screens over which the mud passes removes larger particle size solids (e.g., in the 200 to 700 micron size range) while allowing the drilling fluid and smaller particle size solids to pass through the screen. Solids, which are discarded from the top of the shaker screen, discharge into a pit or onto a conveyor for further treatment or disposal and the underflow drilling fluid flows into the tank below.
A common means to secure the screen in the shaker is through the use of a wedge block. A wedge block is typically inserted between the screen and a bracket located along the inside walls of the shaker. The wedge block is pushed further back under or into the bracket, in turn pushing the wedge downward onto the screen and onto the shaker. Two wedges are typically used per screen, but other combinations of wedges may be utilized.
A common means to seal the screen in the shaker is through the use of gaskets secured to the shaker at the screen interface. The gasket is typically secured to the shaker with various fasteners that wear out due to contact with the drilling fluid and solids. Thus, maintenance is required to replace worn gaskets and/or fasteners. Replacing the gaskets is time- and labor-intensive—the shaker must be taken offline, the wedge blocks removed, the screens removed, the fasteners ground off, the old gasket material removed, and the new gaskets installed with new fasteners, and then the screens and wedge blocks reinstalled.
Accordingly, there remains a need in the art for a shaker screen and sealing gasket capable of easy and efficient replacement, while retaining the necessary securing and sealing properties within a shaker device.